Use of water-soluble polymers as dispersing agents for aqueous suspensions of calcium carbonate aqueous suspensions obtained and their uses

ABSTRACT

The invention relates to the use of homopolymers and/or water-soluble copolymers of acrylic acid with one or more acrylic, vinyl or allylic monomers as dispersing agents for aqueous suspensions of mineral particles issuing from a mechanical and/or thermal reconcentration step following upon a step of wet grinding without the use of a dispersant and at low concentration in terms of dry matter.  
     The invention also relates to the said aqueous suspensions and their uses in the fields of paper, paint, fillers for synthetic resins and rubbers, detergent and cleaning formulations, ceramics, drilling fluids, cements, plasters and other fields of application in civil engineering and the construction industry.

[0001] The invention relates to the use of homopolymers and/orwater-soluble copolymers of acrylic acid with one or more acrylic, vinylor allylic monomers as dispersing agents for aqueous suspensions ofcalcium carbonate.

[0002] The invention also relates to the said aqueous suspensions ofcalcium carbonate and their uses in the fields of paper, like notablythe manufacture or coating of paper, those of paint, fillers forsynthetic resins and rubbers, detergent and cleaning formulations, andany other field using said suspensions such as notably ceramics,drilling fluids, cements, plasters and other fields of application incivil engineering and the construction industry.

[0003] For a long time already, persons skilled in the art have knownabout the use of grinding and/or dispersing agents for aqueoussuspensions of mineral particles constituted by acrylic polymers and/orcopolymers, of low molecular weight, totally or partially neutralized byvarious neutralizing agents (FR 2 603 042, EP 0 100 947, EP 0 127 388,EP 0 129 329 and EP 0 542 644).

[0004] Persons skilled in the art also know about the use of grindingand/or dispersing agents constituted by the fraction of acrylic polymersand/or copolymers whose specific viscosity is between 0.3 and 0.8(patents FR 2 488 814, EP 0 100 948 and EP 0 542 643).

[0005] But these various types of grinding and/or dispersing agents oflow molecular weight which make it possible to obtain aqueoussuspensions of mineral particles refined and stable over time do notallow the putting back into suspension or redispersal in water ofmineral particles, such as notably calcium carbonate, issuing from amechanical and/or thermal reconcentration step following upon a step ofwet grinding without the use of a dispersant and at low concentration interms of dry matter. Such mineral particles, issuing from thismechanical and/or thermal reconcentration step following upon a step ofwet grinding without the use of a dispersant, pose serious usageproblems for persons skilled in the art who must disperse these mineralparticles in the form of suspensions at very high concentration in termsof dry matter in order to be able to offer them to the user in a formwhich can be manipulated by said user.

[0006] Confronted with this problem, the Applicant then found,surprisingly, that the selection of homopolymers of acrylic acid and/orwater-soluble copolymers of acrylic acid with one or more acrylic, vinylor allylic monomers of a different and higher molecular weight than allthe literature known to date teaches (and notably the patent applicationEP 0 850 685), makes it possible to put into aqueous suspension themineral particles issuing from this mechanical and/or thermalreconcentration step following upon a step of wet grinding without theuse of a dispersant and at low concentration in terms of dry matter.

[0007] By a step of wet grinding without the use of a dispersant, theapplicant means a step of wet grinding without any dispersant butpossibly with small quantities of flocculating agent up to 500 ppm.

[0008] Thus, one of the aims of the invention is the use of homopolymersof acrylic acid and/or water-soluble copolymers of acrylic acid with oneor more acrylic, vinyl or allylic monomers of a molecular weightcorresponding to a viscosity index with a value from 0.08 to 0.80, andpreferentially from 0.20 to 0.60, as dispersing agents for aqueoussuspensions of mineral particles issuing from a mechanical and/orthermal reconcentration step following upon a step of wet grindingwithout the use of a dispersant and at low concentration in terms of drymatter.

[0009] Similarly, another aim of the invention is to provide adispersing agent for aqueous suspensions of mineral particles issuingfrom a mechanical and/or thermal reconcentration step following upon astep of wet grinding without the use of a dispersant and at lowconcentration in terms of dry matter.

[0010] An additional aim of the invention is to provide a method ofputting said mineral particles into aqueous suspension using theselection of homopolymers of acrylic acid and/or water-solublecopolymers of acrylic acid with one or more acrylic, vinyl or allylicmonomers of a molecular weight corresponding to a viscosity index with avalue from 0.08 to 0.80, and preferentially from 0.20 to 0.60.

[0011] Another aim of the invention, besides those already mentioned, isto provide aqueous suspensions of refined mineral materials obtained bythe aforementioned method, and characterised in that they contain from0.1% to 2% by dry weight, and preferentially from 0.3% to 1.0% by dryweight, with respect to the dry weight of mineral material, of aqueoussuspension dispersing agent according to the invention.

[0012] Finally, an additional aim of the invention concerns the use ofthese mineral aqueous suspensions in the fields of mass filling andcoating of paper as well as those of paint, ceramics, drilling fluids,fillers for synthetic resins and rubbers, detergent and cleaningformulations, and any other field using said suspensions such as notablycements, plasters and other fields of application in civil engineeringand the construction industry.

[0013] These aims are achieved by virtue of the use according to theinvention of homopolymers of acrylic acid and/or water-solublecopolymers of acrylic acid with one or more acrylic, vinyl or allylicmonomers of a molecular weight corresponding to a viscosity index with avalue from 0.08 to 0.80, and preferentially from 0.20 to 0.60.

[0014] These homopolymers and/or copolymers result from the variousknown methods of radical polymerization using the polymerizationinitiators well known to persons skilled in the art such as, forexample, hydroxylamine-based compounds or also using the polymerizationinitiators such as peroxides like notably hydrogen peroxide, tert-butylhydroperoxide or the persalts like notably sodium persulphate, ammoniumpersulphate, potassium persulphate or analogues, or also sodiumhypophosphite, hypophosphorous acid or again also phosphorous acidand/or their salts in the possible presence of metallic salts forexample of iron or copper in a polymerization medium which can be water,methanol, ethanol, propanol, isopropanol, butanols, or their mixtures oralso dimethylformamide, dimethylsulphoxide, tetrahydrofurane, acetone,methyl ethyl ketone, ethyl acetate, butyl acetate, hexane, heptane,benzene, toluene, xylene, and possibly in the presence of molecular masscontrollers also referred to as chain transfer agents such as notablymercaptoethanol, thioglycolic acid and its esters, n-dodecyl mercaptan,acetic, tartaric, lactic, citric, gluconic or glucoheptonic acids,2-mercaptopropionic acid, thiodiethanol, halogenated solvents likecarbon tetrachloride, chloroform, methylene chloride, the ethers ofmonopropylene glycol, or their mixtures and analogues.

[0015] These homopolymers and/or copolymers used as dispersing agentsaccording to the invention result from the various aforementionedmethods of radical polymerization of one at least of the monomers chosenfrom among acrylic acid, methacrylic acid, itaconic acid, crotonic acid,fumaric acid, isocrotonic, aconitic, mesaconic, sinapic, undecylenic,angelic or canellic acid, and/or acrylamido methyl propane sulphonicacid in acid or partially neutralized form, or also from amongacrylamide, methacrylamide, the esters of acrylic or methacrylic acidssuch as notably ethyl acrylate, butyl acrylate, methyl methacrylate,phosphate of acrylate or methacrylate of ethylene or propylene glycol oralso again from among vinylpyrrolidone, vinylcaprolactame, isobutylene,diisobutylene, vinyl acetate, styrene, alphamethylstyrene, styrenesodium sulphonate vinylmethylether, or the allylics such as notablyallylamine and its derivatives.

[0016] These homopolymers and/or copolymers used as dispersing agentsaccording to the invention are partially or totally neutralized by oneor more neutralizing agents having a monovalent function and possibly apolyvalent function.

[0017] The neutralizing agents having a monovalent function are chosenfrom the group constituted by the compounds containing alkaline cations,in particular sodium and potassium, or also lithium, ammonium, or againthe aliphatic and/or cyclic primary or secondary amines such as forexample the ethanolamines, mono and diethylamine or alsocyclohexylamine.

[0018] The neutralizing agents having a polyvalent function are chosenfrom the group constituted by the compounds containing alkaline-earthdivalent cations, in particular magnesium and calcium, or also zinc, andlikewise by the trivalent cations, including in particular aluminium, oralso by certain compounds containing higher-valency cations.

[0019] The homopolymers and/or copolymers designed to be used accordingto the invention as dispersing agents in water for mineral particlesissuing from a mechanical and/or thermal reconcentration step followingupon a step of wet grinding without the use of a dispersant and at lowconcentration in terms of dry matter are selected from among thehomopolymers or copolymers having a molecular weight corresponding to aviscosity index with a value from 0.08 to 0.80, and preferentially from0.20 to 0.60.

[0020] The molecular weight of the homopolymers or copolymers ismeasured on the form of the polymer salified with soda and according tothe procedure described below and will be referred to as the viscosityindex throughout the remainder of the present application.

[0021] To do this, the acid form of the compound whose viscosity indexit is necessary to determine is 100% neutralized with soda and thendiluted at 50 g/l in bipermutated water. This parent solution, whichthen has a concentration denoted c₀, is subjected to the followingdilutions: (2/3)c₀, (l/2)c₀, (1/3)c₀, (1/4)c₀, (1/6)c₀, (1/12)c₀,(1/18)c₀, (1/24)c₀, (1/36)c₀.

[0022] The specific viscosity for each solution is then determined bymeans of a Schott AVS/500 viscometer equipped with an Ubbelohde tube ofreference 53010/I and constant 0.01 and the specific viscosity curve isplotted as a function of the concentration.

[0023] The linear part of the curve makes it possible to obtain theviscosity index according to the equation

Viscosity index=Limit of the specific viscosity when the concentrationtends to zero.

[0024] The refined mineral substances to be put into suspensionaccording to the invention are chosen from among the synthetic calciumcarbonates or the natural calcium carbonates such as notably chalk,calcite, marble or also dolomite or their mixtures.

[0025] Thus, the use according to the invention of a selection ofhomopolymers of acrylic acid and/or water-soluble copolymers of acrylicacid with one or more acrylic, vinyl or allylic monomers and thedevelopment of a dispersing agent according to the invention permits theputting into suspension of mineral substances issuing from a mechanicaland/or thermal reconcentration step following upon a step of wetgrinding without the use of a dispersant and at low concentration interms of dry matter and thus allows the obtaining of aqueous suspensionsof refined mineral materials obtained by the aforementioned method andcontaining said dispersing agent according to the invention.

[0026] In practice, the operation of dispersing or putting into aqueoussuspension of said mineral substances consists of adding, underagitation, the necessary amount of dispersing agent according to theinvention so as to obtain an aqueous suspension of said mineralmaterials, issuing from a mechanical and/or thermal reconcentrationstep, having a concentration in terms of dry matter of at least 60% witha Brookfield viscosity strictly less than 2000 mPa.s measured at 100 rpmimmediately after the putting into suspension and a Brookfield viscositystrictly less than 20,000 mPa.s, measured at 10 rpm after eight days'storage without agitation, that is to say so as to obtain an aqueoussuspension of said mineral materials highly concentrated in terms of drymatter which remains able to be manipulated by the user even after astorage of a number of days and without agitation.

[0027] The scope and advantage of the invention will be betterunderstood by virtue of the following examples, which are notrestrictive in any respect.

EXAMPLE 1

[0028] This example relates to the selection of the molecular weight(expressed by the viscosity index) of the dispersing agent allowing theputting into aqueous suspension of natural calcium carbonate ground withno dispersant at a granulometry of which 73% of the particles have adiameter less than one micrometer determined by the Micromeriticscompany Sedigraph 5100 measurement and issuing from a mechanicalreconcentration of the centrifugation type following upon this wetgrinding at low concentration in terms of dry matter and with nodispersant.

[0029] This natural calcium carbonate is a marble.

[0030] For each test, the aqueous suspension of marble was prepared byintroduction, into the filter cake issuing from the centrifugation, of0.4% by dry weight of dispersing agent to be tested with respect to thedry weight of said filter cake to be put into suspension so as to obtainan aqueous suspension of calcium carbonate at a concentration in termsof dry matter equal to 61%.

[0031] After twenty minutes' agitation, a sample of the calciumcarbonate suspension obtained is retrieved in a flask and its Brookfieldviscosity is measured by means of an RVT type Brookfield viscometer, ata temperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

[0032] After a time of 8 days in the flask, the Brookfield viscosity ofthe suspension is measured by introduction, into the non-agitated flask,of the appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

[0033] The different homopolymers tested are:

[0034] Test 1:

[0035] This test, which illustrates the prior art, uses a totallyneutralized sodium polyacrylate with viscosity index equal to 0.04measured according to the aforementioned procedure.

[0036] Test 2:

[0037] This test, which illustrates the prior art, uses a mixedpolyacrylate of magnesium and sodium (50% magnesium-50% sodium by mole)whose salified with soda form has a viscosity index equal to 0.04measured according to the aforementioned procedure.

[0038] Test 3:

[0039] This test, which illustrates the prior art, uses a totallyneutralized sodium polyacrylate with viscosity index equal to 0.07measured according to the aforementioned procedure.

[0040] Test 4:

[0041] This test, which illustrates the invention, uses a totallyneutralized sodium polyacrylate with viscosity index equal to 0.10measured according to the aforementioned procedure.

[0042] Test 5:

[0043] This test, which illustrates the invention, uses a totallyneutralized sodium polyacrylate with viscosity index equal to 0.31measured according to the aforementioned procedure.

[0044] Test 6:

[0045] This test, which illustrates the invention, uses a totallyneutralized sodium polyacrylate with viscosity index equal to 0.39measured according to the aforementioned procedure.

[0046] Test 7:

[0047] This test, which illustrates the invention, uses a totallyneutralized sodium polyacrylate with viscosity index equal to 0.44measured according to the aforementioned procedure.

[0048] Test 8:

[0049] This test, which illustrates the invention, uses a totallyneutralized sodium polyacrylate with viscosity index equal to 0.75measured according to the aforementioned procedure.

[0050] Test 9:

[0051] This test, which illustrates a field outside the invention, usesa totally neutralized sodium polyacrylate with viscosity index equal to0.83 measured according to the aforementioned procedure.

[0052] All the experimental results are recorded in the followingTable 1. TABLE 1 Brookfield viscosity Brookfield viscosity ViscosityComposition Dose T = 0 T = 8D PRE-AG Tests index (%) (%) 100 rpm (mPa ·s) 10 rpm (mPa · s) 1 Prior art 0.04 AA 100 0.4 6000 34000 2 Prior art0.04 AA 100 0.4 3500 32000 3 Prior art 0.07 AA 100 0.4 2600 27000 4Invention 0.10 AA 100 0.4 1800 19000 5 Invention 0.31 AA 100 0.4 8809000 6 Invention 0.39 AA 100 0.4 280 6000 7 Invention 0.44 AA 100 0.4320 7000 8 Invention 0.75 AA 100 0.4 350 12000 9 Outside the 0.83 AA 1000.4 440 21000 invention

[0053] The reading of Table 1 allows it to be noted that, contrary toany expectation of persons skilled in the art, the homopolymers ofacrylic acid having a viscosity index selected from the interval between0.08 and 0.80 make it possible to put into suspension a calciumcarbonate issuing from a mechanical reconcentration of thecentrifugation type following upon a wet grinding at low concentrationin terms of dry matter and with no dispersant.

EXAMPLE 2

[0054] This example relates to the use of copolymers according to theinvention as dispersing agents allowing the putting into aqueoussuspension of natural calcium carbonate ground with no dispersant at agranulometry of which 73% of the particles have a diameter less than onemicrometer determined by the Micromeritics company Sedigraph 5100measurement and issuing from a mechanical reconcentration of thecentrifugation type following upon this wet grinding at lowconcentration in terms of dry matter and with no dispersant.

[0055] This natural calcium carbonate is a marble.

[0056] The dispersing agents of the different tests of the example aretested with the same equipment and the same operating method as in theprevious example.

[0057] Test 10:

[0058] This test, which illustrates a field outside the invention, usesa copolymer, 100% neutralized with soda, with viscosity index equal to0.05 measured according to the aforementioned procedure and composed, interms of weight percentage, of 70% acrylic acid and 30% methacrylicacid.

[0059] Test 11:

[0060] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.12 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

[0061] Test 12:

[0062] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.73 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

[0063] Test 13:

[0064] This test, which illustrates a field outside the invention, usesa copolymer, 100% neutralized with soda, with viscosity index equal to0.06 measured according to the aforementioned procedure and composed, interms of weight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

[0065] Test 14:

[0066] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.08 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

[0067] Test 15:

[0068] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.11 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

[0069] Test 16:

[0070] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.17 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

[0071] Test 17:

[0072] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.26 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

[0073] Test 18:

[0074] This test, which illustrates a field outside the invention, usesa copolymer, 100% neutralized with soda, with viscosity index equal to0.81 measured according to the aforementioned procedure and composed, interms of weight percentage, of 80% acrylic acid and 20% ethylene glycolmethacrylate phosphate.

[0075] Test 19:

[0076] This test, which illustrates a field outside the invention, usesa copolymer, 100% neutralized with soda, with viscosity index equal to0.06 measured according to the aforementioned procedure and composed, interms of weight percentage, of 70% acrylic acid and 30% acrylamidomethyl propane sulphonic acid.

[0077] Test 20:

[0078] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.10 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

[0079] Test 21:

[0080] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.14 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

[0081] Test 22:

[0082] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.35 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

[0083] Test 23:

[0084] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.48 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

[0085] Test 24:

[0086] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.54 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% acrylamido methyl propanesulphonic acid.

[0087] Test 25:

[0088] This test, which illustrates a field outside the invention, usesa copolymer, 100% neutralized with soda, with viscosity index equal to0.07 measured according to the aforementioned procedure and composed, interms of weight percentage, of 30% acrylic acid and 70% acrylamide.

[0089] Test 26:

[0090] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.15 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

[0091] Test 27:

[0092] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.43 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

[0093] Test 28:

[0094] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.56 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

[0095] Test 29:

[0096] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.67 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 30% acrylic acid and 70% acrylamide.

[0097] Test 30:

[0098] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.33 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylamide.

[0099] Test 31:

[0100] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.28 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% styrene sodiumsulphonate.

[0101] Test 32:

[0102] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.48 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% vinylpyrrolidone.

[0103] All the experimental results are recorded in the following Table2. TABLE 2 Brookfield viscosity Brookfield viscosity ViscosityComposition Dose T = 0 T = 8D PRE-AG Tests index (%) (%) 100 rpm (mPa ·s) 10 rpm (mPa · s) 10 Outside the invention 0.05 AA 70 MAA 30 0.4 230019000 11 Invention 0.12 AA 70 MAA 30 0.4 1260 15000 12 Invention 0.73 AA70 MAA 30 0.4 600 9000 13 Outside the invention 0.06 AA 80 EGMAPO₄ 200.4 1200 22000 14 Invention 0.08 AA 80 EGMAPO₄ 20 0.4 730 8000 15Invention 0.11 AA 80 EGMAPO₄ 20 0.4 600 7000 16 Invention 0.17 AA 80EGMAPO₄ 20 0.4 420 9000 17 Invention 0.26 AA 80 EGMAPO₄ 20 0.4 450 800018 Outside the invention 0.81 AA 80 EGMAPO₄ 20 0.4 550 33000 19 Outsidethe invention 0.06 AA 70 AMPS 30 0.4 1150 22000 20 Invention 0.10 AA 70AMPS 30 0.4 850 9000 21 Invention 0.14 AA 70 AMPS 30 0.4 670 9000 22Invention 0.35 AA 70 AMPS 30 0.4 540 5000 23 Invention 0.48 AA 70 AMPS30 0.4 520 10000 24 Invention 0.54 AA 70 AMPS 30 0.4 700 16000 25Outside the invention 0.07 AAM 70 AA 30 0.4 Dispersion impossible 26Invention 0.15 AAM 70 AA 30 0.4 1440 11000 27 Invention 0.43 AAM 70 AA30 0.4 868 10450 28 Invention 0.56 AAM 70 AA 30 0.4 780 10000 29Invention 0.67 AAM 70 AA 30 0.4 800 12000 30 Invention 0.33 AA 70 MAAM30 0.4 550 11000 31 Invention 0.28 AA 70 SSNa 30 0.4 700 10500 32Invention 0.48 AA 80 VP 20 0.4 900 11000

[0104] The reading of Table 2 allows it to be noted that the copolymersof acrylic acid having a viscosity index selected from the intervalbetween 0.08 and 0.80 make it possible to put into suspension a calciumcarbonate issuing from a mechanical reconcentration of thecentrifugation type following upon a wet grinding at low concentrationin terms of dry matter and with no dispersant.

EXAMPLE 3

[0105] This example relates to the use of copolymers according to theinvention as dispersing agents allowing the putting into aqueoussuspension of natural calcium carbonate ground with no dispersant at agranulometry of which 61% of the particles have a diameter less than onemicrometer determined by the Micromeritics company Sedigraph 5100measurement and issuing from a mechanical reconcentration of thecentrifugation type following upon this wet grinding at lowconcentration in terms of dry matter and with no dispersant.

[0106] This natural calcium carbonate is a chalk.

[0107] The dispersing agents of the different tests of the example aretested with the same equipment and the same operating method as in theprevious example, with the exception of the dry matter content of theaqueous suspension of calcium carbonate obtained which is 62% instead of61%, and the exception of the test 39, where 1.0% by dry weight ofdispersing agent is tested.

[0108] Test 33:

[0109] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.15 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% itaconic acid.

[0110] Test 34:

[0111] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.73 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% ethyl acrylate.

[0112] Test 35:

[0113] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.21 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

[0114] Test 36:

[0115] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.42 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

[0116] Test 37:

[0117] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.70 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 70% acrylic acid and 30% methacrylic acid.

[0118] Test 38:

[0119] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.11 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 80% acrylic acid and 20% allylamine.

[0120] Test 39:

[0121] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.10 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 15% acrylic acid, 60% methacrylic acid, 12.5%styrene and 12.5% butyl acrylate.

[0122] Test 40:

[0123] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.54 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 90% acrylic acid and 10% vinyl acetate.

[0124] Test 41:

[0125] This test, which illustrates the invention, uses a copolymer,100% neutralized with soda, with viscosity index equal to 0.22 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 85% acrylic acid and 15% methyl methacrylate.

[0126] All the experimental results are recorded in the following Table3. TABLE 3 Brookfield viscosity Brookfield viscosity ViscosityComposition Dose T = 0 T = 8D PRE-AG Tests index (%) (%) 100 rpm (mPa ·s) 10 rpm (mPa · s) 33 Invention 0.15 AA 80 ITCA 20 0.4 225 7000 34Invention 0.73 AA 70 EA 30 0.4 960 16000 35 Invention 0.21 AA 70 MAA 300.4 1100 12000 36 Invention 0.42 AA 70 MAA 30 0.4 850 13500 37 Invention0.70 AA 70 MAA 30 0.4 655 10000 38 Invention 0.11 AA 80 ALLYL 20 0.4 65510000 39 Invention 0.10 AA 15 MAA 60 1.0 800 10000 STY 12.5 40 Invention0.54 AA 90 VAC 10 0.4 600 13000 BUA 12.5 41 Invention 0.22 AA 85 MMA 150.4 1250 15000

[0127] The reading of Table 3 allows it to be noted that the copolymersof acrylic acid having a viscosity index selected from the intervalbetween 0.08 and 0.80 make it possible to put into suspension a calciumcarbonate issuing from a mechanical reconcentration of thecentrifugation type following upon a wet grinding at low concentrationin terms of dry matter and with no dispersant, and with granulometrydifferent from that of Example 2.

EXAMPLE 4

[0128] This example relates to the proportion of polymer used as adispersing agent allowing the putting into aqueous suspension of naturalcalcium carbonate ground with no dispersant at a granulometry of which61% of the particles have a diameter less than one micrometer determinedby the Micromeritics company Sedigraph 5100 measurement and issuing froma mechanical reconcentration of the centrifugation type following uponthis wet grinding at low concentration in terms of dry matter and withno dispersant.

[0129] This natural calcium carbonate is a marble.

[0130] For this test (test 42), the aqueous suspension of marble wasprepared by introduction, into the filter cake issuing from thecentrifugation, of 2.0% by dry weight, with respect to the dry weight ofsaid filter cake to be put into suspension, of a copolymer 100%neutralized with soda with viscosity index equal to 0.13 measuredaccording to the aforementioned procedure and composed, in terms ofweight percentage, of 41% styrene, 15% butyl acrylate, 36% methacrylicacid and 8% acrylic acid, so as to obtain an aqueous suspension ofcalcium carbonate at a concentration in terms of dry matter equal to62%.

[0131] After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

[0132] The following result is obtained: Brookfield viscosity equal to1550 mPa.s.

[0133] After a time of 8 days in the flask, the Brookfield viscosity ofthe suspension is measured by introduction, into the non-agitated flask,of the appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm with theappropriate spindle (PRE-AG viscosity Brookfield viscosity beforeagitation).

[0134] The following result is obtained: Brookfield viscosity equal to3000 mPa.s.

EXAMPLE 5

[0135] This example relates to the degree of neutralization and thenature of the neutralization of the polymer used as a dispersing agentallowing the putting into aqueous suspension of natural calciumcarbonate ground with no dispersant at a granulometry of which 73% ofthe particles have a diameter less than one micrometer determined by theMicromeritics company Sedigraph 5100 measurement and issuing from amechanical reconcentration of the centrifugation type following uponthis wet grinding at low concentration in terms of dry matter and withno dispersant.

[0136] This natural calcium carbonate is a marble.

[0137] For each test, the aqueous suspension of marble was prepared byintroduction, into the filter cake issuing from the centrifugation, of0.8% by dry weight of dispersing agent to be tested with respect to thedry weight of said filter cake to be put into suspension so as to obtainan aqueous suspension of calcium carbonate at a concentration in termsof dry matter equal to 63%.

[0138] After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

[0139] After a time of 8 days in the flask, the Brookfield viscosity ofthe suspension is measured by introduction, into the non-agitated flask,of the appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

[0140] The different homopolymers of acrylic acid tested are:

[0141] Test 43:

[0142] This test, which illustrates the invention, uses a mixedpolyacrylate of calcium and sodium (15% calcium-85% sodium by mole), thesalified with soda form of which has a viscosity index equal to 0.39measured according to the aforementioned procedure.

[0143] Test 44:

[0144] This test, which illustrates the invention, uses a mixedpolyacrylate of magnesium and sodium (15% magnesium 85% sodium by mole),the salified with soda form of which has a viscosity index equal to 0.39measured according to the aforementioned procedure.

[0145] Test 45:

[0146] This test, which illustrates the invention, uses a polyacrylatepartially neutralized with soda (80% molar) with viscosity index equalto 0.39 measured according to the aforementioned procedure.

[0147] Test 46:

[0148] This test, which illustrates the invention, uses a partiallyneutralized mixed polyacrylate of calcium and sodium (15% calcium-65%sodium by mole), the salified with soda form of which has a viscosityindex equal to 0.39 measured according to the aforementioned procedure.

[0149] Test 47:

[0150] This test, which illustrates the invention, uses a partiallyneutralized mixed polyacrylate of magnesium and sodium (15%magnesium-65% sodium by mole), the salified with soda form of which hasa viscosity index equal to 0.39 measured according to the aforementionedprocedure.

[0151] All the experimental results are recorded in the following Table4. TABLE 4 Brookfield viscosity Brookfield viscosity Dose T = 0 T = 8DPRE-AG Tests Neutralization (%) 100 rpm (mPa · s) 10 rpm (mPa · s) 43Invention 85% Na 15% Ca 0.8 840 8000 44 Invention 85% Na 15% Mg 0.8 87010000 45 Invention 80% Na — 0.8 1020 7000 46 Invention 65% Na 15% Ca 0.8920 5000 47 Invention 65% Na 15% Mg 0.8 1550 6000

[0152] The reading of Table 4 allows it to be noted that thehomopolymers of acrylic acid having a viscosity index selected from theinterval between 0.08 and 0.80, whether partially or totally neutralizedby at least one neutralizing agent having a monovalent function andpossibly by an agent having a polyvalent function, make it possible toput into suspension a calcium carbonate issuing from a mechanicalreconcentration of the centrifugation type following upon a wet grindingat low concentration in terms of dry matter and with no dispersant.

EXAMPLE 6

[0153] This example relates to the nature of the neutralizing agent,having a monovalent function, of the polymer used as a dispersing agentallowing the putting into aqueous suspension of natural calciumcarbonate ground with no dispersant at a granulometry of which 73% ofthe particles have a diameter less than one micrometer determined by theMicromeritics company Sedigraph 5100 measurement and issuing from amechanical reconcentration of the filter press type following upon thiswet grinding at low concentration in terms of dry matter and with nodispersant.

[0154] This natural calcium carbonate is a marble.

[0155] For each test, the aqueous suspension of marble was prepared byintroduction, into the filter cake issuing from the filtration, of 0.4%by dry weight of dispersing agent to be tested with respect to the dryweight of said filter cake to be put into suspension so as to obtain anaqueous suspension of calcium carbonate at a concentration in terms ofdry matter equal to 63%.

[0156] After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

[0157] After a time of 8 days in the flask, the Brookfield viscosity ofthe suspension is measured by introduction, into the non-agitated flask,of the appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

[0158] The different homopolymers of acrylic acid tested are:

[0159] Test 48:

[0160] This test, which illustrates the invention, uses a totallyneutralized potassium polyacrylate, the salified with soda form of whichhas a viscosity index equal to 0.39 measured according to theaforementioned procedure.

[0161] Test 49:

[0162] This test, which illustrates the invention, uses a totallyneutralized lithium polyacrylate, the salified with soda form of whichhas a viscosity index equal to 0.39 measured according to theaforementioned procedure.

[0163] Test 50:

[0164] This test, which illustrates the invention, uses a totallyneutralized ammonium polyacrylate, the salified with soda form of whichhas a viscosity index equal to 0.39 measured according to theaforementioned procedure.

[0165] All the experimental results are recorded in the following Table5. TABLE 5 Brookfield viscosity Brookfield viscosity Dose T = 0 T = 8DPRE-AG Tests Neutralization (%) 100 rpm (mPa · s) 10 rpm (mPa · s) 48Invention 100% KOH 0.4 130 8000 49 Invention 100% LiOH 0.4 180 3500 50Invention 100% NH₄OH 0.4 120 6000

[0166] The reading of Table 5 allows it to be noted that thehomopolymers of acrylic acid having a viscosity index selected from theinterval between 0.08 and 0.80 make it possible to put into suspension acalcium carbonate issuing from a mechanical reconcentration of thefilter press type following upon a wet grinding at low concentration interms of dry matter and with no dispersant, whatever the nature of theneutralizing agent having a monovalent function.

EXAMPLE 7

[0167] This example relates to the use of polymers according to theinvention as dispersing agents allowing the putting into aqueoussuspension of natural calcium carbonate ground with no dispersant at agranulometry of which 73% of the particles have a diameter less than onemicrometer determined by the Micromeritics company Sedigraph 5100measurement and issuing from a thermal reconcentration following uponthis wet grinding at low concentration in terms of dry matter and withno dispersant.

[0168] This natural calcium carbonate is a marble.

[0169] For this test (test 51), the aqueous suspension of marble wasprepared by introduction, into the thermally reconcentrated suspension,of 1.0% by dry weight, with respect to the dry weight of said filtercake to be put into suspension, of a totally neutralized sodiumpolyacrylate with viscosity index equal to 0.39 measured according tothe aforementioned procedure, so as to obtain an aqueous suspension ofcalcium carbonate at a concentration in terms of dry matter equal to72%.

[0170] After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

[0171] The following result is obtained: Brookfield viscosity equal to700 mPa.s.

[0172] After a time of 8 days in the flask, the Brookfield viscosity ofthe suspension is measured by introduction, into the non-agitated flask,of the appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm with theappropriate spindle (PRE-AG viscosity=Brookfield viscosity beforeagitation).

[0173] The following result is obtained: Brookfield viscosity equal to11,000 mPa.s.

[0174] This result allows it to be noted that the polymers of acrylicacid having a viscosity index selected from the interval between 0.08and 0.80 make it possible to put into suspension, highly concentrated interms of dry matter, a calcium carbonate issuing from a thermalreconcentration following upon a wet grinding at low concentration interms of dry matter and with no dispersant.

EXAMPLE 8

[0175] This example relates to the use of polymers according to theinvention as dispersing agents allowing the putting into aqueoussuspension of natural calcium carbonate ground with no dispersant at agranulometry of which 73% of the particles have a diameter less than onemicrometer determined by the Micromeritics company Sedigraph 5100measurement and issuing from a mechanical reconcentration of thecentrifugation type followed by a thermal reconcentration following uponthis wet grinding at low concentration in terms of dry matter and withno dispersant.

[0176] This natural calcium carbonate is a marble.

[0177] For this test (test 52), the aqueous suspension of marble wasprepared by introduction, into the filter cake issuing from themechanical and then thermal reconcentration, of 0.8% by dry weight, withrespect to the dry weight of said filter cake to be put into suspension,of a copolymer totally neutralized with soda, with viscosity index equalto 0.15 and composed of 80% by weight of acrylic acid and 20% by weightof itaconic acid, so as to obtain an aqueous suspension of calciumcarbonate at a concentration in terms of dry matter equal to 72%.

[0178] After 20 minutes' agitation, a sample of the calcium carbonatesuspension obtained is retrieved in a flask and its Brookfield viscosityis measured by means of an RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 100 rpm with theappropriate spindle.

[0179] The following result is obtained: Brookfield viscosity (100rpm)=390 mPa.s.

[0180] After a time of 8 days in the flask, the Brookfield viscosity ofthe suspension is measured by introduction, into the non-agitated flask,of the appropriate spindle of the RVT type Brookfield viscometer, at atemperature of 25° C. and a speed of rotation of 10 rpm (PRE-AGviscosity=Brookfield viscosity before agitation).

[0181] The following result is obtained: Brookfield viscosity (10rpm)=4,000 mPa.s.

[0182] This result allows it to be noted that the acrylic acid/itaconicacid copolymer having a viscosity index selected from the intervalbetween 0.08 and 0.80 makes it possible to put into suspension, highlyconcentrated in terms of dry matter, a calcium carbonate issuing from amechanical and then thermal reconcentration following upon a wetgrinding at low concentration in terms of dry matter and with nodispersant.

EXAMPLE 9

[0183] This example relates to the use of aqueous suspensions of mineralfillers as proposed by the invention in the manufacture of coatingcolour for paper.

[0184] To this end, the coating colours are prepared by mixing theaqueous suspensions of mineral fillers to be tested in water with theother constituents of the coating colour, the composition by weight ofwhich is as follows:

[0185] 100 parts of aqueous suspensions to be tested with a content of65% in dry substance

[0186] 12 parts of a carboxylated styrene-butadiene latex marketed byDow Chemical under the name of DL 905

[0187] 0.5 part of carboxymethyl cellulose sold by Metsa Serla under thename of Finnfix 5,

[0188] the content of dry substance being in the order of 64.5% and thepH being equal to 8.4.

[0189] Brookfield viscosity measurements are then taken on the coatingcolours prepared in this manner, at ambient temperature and at 20revolutions per minute, 50 revolutions per minute and 100 revolutionsper minute using a Brookfield viscometer of the DVII type fitted withthe appropriate spindle.

[0190] Test 53:

[0191] This test, illustrating the invention, uses an aqueous suspensionof calcium carbonate according to test n° 6.

[0192] The results of all the experiments are set out in table 6 below.TABLE 6 Brookfield viscosity in mPa.s. Test n° 20 r/min 50 r/min 100r/min Invention 53 3650 2000 1590

[0193] Table 6 shows that an aqueous suspension of calcium carbonateaccording to the invention can be used in the manufacture of coatingcolour for paper.

EXAMPLE 10

[0194] This example relates to the use of aqueous suspensions of mineralfillers as proposed by the invention in the mass filling for paper. Tothis end, sheets of paper are made from a cellulose pulp of SR 23 degreecontaining a woodless sulphate paste and fibres comprising 80% birch and20% pine. 45 g dry weight of this pulp are then diluted in 10 liters ofwater in the presence of about 15 g dry weight of the filler compositionto be tested to produce experimentally a filler content of 20%. After 15minutes of agitation and adding 0.06% by dry weight, relative to the dryweight of paper, a retention agent of the polyacrylamide type, a sheetis made with a grammage equal to 75 g/m² and filled to 20%. The deviceused to make the sheet is a Rapid-Kothen 20.12 MC modelby Haage.

[0195] The sheets prepared in this manner are dried for 400 seconds at92° C. and in a vacuum of 940 mbar. The filler content is controlled byanalysing the ashes.

[0196] The value for opacity of the obtained paper sheet is thendetermined using the DIN 53146 standard.

[0197] Test 54:

[0198] This test, which illustrates the invention, uses the aqueoussuspension of calcium carbonate according to test 6. The value foropacity, measured using the DIN 53146 standard, is 88.

[0199] This value shows that anyone of the aqueous suspension of calciumcarbonate, according to the invention, can be used as a mass filling forpaper.

EXAMPLE 11

[0200] This example relates to the use of aqueous suspensions of mineralfillers as proposed by the invention in the field of paint and moreparticularly water-based glazed paint. To do that, test 55 according tothe invention is carried out.

[0201] For this test, the constituents of the said water-based glazedpaint were added in succession, these being: 40 g of monopropyleneglycol 2 g of a biocide, marketed by TROY under the name of MERGAL ™ K6N1 g of an anti-foaming agent marketed by HENKEL under the name ofNOPCO ™ NDW 217,4 g of the calcium carbonate aqueous suspensionaccording to test 6 and with a solid content of 65% 200 g of rutiletitanium oxide marked by MILLENNIUM under the name TIONA ™ RL 68 450 gof a styrene-acrylic binder in dispersion, marketed by RHODIA under thename of RHODOPAS ™ DS 910 30 g of butyldiglycol 1 g of Nopco ™ NDW 3 gof 28% ammonia 4 g of a thickening agent marketed by COATEX under thename COATEX BR100P and 49,6 g of water.

[0202] After agitating the aqueous composition made up in this way for afew minutes at a pH equal to 8.5 the Brookfield viscosities of thedifferent compositions are measured at 25° C. and at 10 revolutions perminute and 100 revolutions per minute using a standard RVT Brookfieldviscometer fitted with the requisite spindle.

[0203] The Theological stability of the formula over time and in termsof temperature is determined by measuring the Brookfield viscosities at10 revolutions per minute and at 100 revolutions per minute at 25° C. ofthis same formula after storing at ambient temperature without agitationfor 24 hours and then after storing for one week at ambient temperature.

[0204] The rheological stability is also determined by the ICI viscositywhich is a high shear viscosity measured with the use of a plan coneviscometer.

[0205] The Stormer KU viscosity is also measured in Krebs Unit with theuse of a Stormer viscometer.

[0206] The obtained results of the different measurements are:

[0207] At t=0 Brookfield viscosity 10 rpm 4000 mPa.s

[0208] Brookfield viscosity 100 rpm=2200 mPa.s

[0209] ICI viscosity=160 mPa.s

[0210] KU Stormer viscosity=97 KU

[0211] At t=24 hours

[0212] Brookfield viscosity 10 rpm=8400 mpa.s

[0213] Brookfield viscosity 100 rpm=4700 mPa.s

[0214] ICI viscosity=130 mpa.s

[0215] KU Stormer viscosity=121 KU

[0216] At t=8 days

[0217] Brookfield viscosity 10 rpm=8200 mPa.s

[0218] Brookfield viscosity 100 rpm=4600 mPa.s

[0219] ICI viscosity=130 mPa.s

[0220] KU Stormer viscosity=121 KU

[0221] The reading of these results shows that anyone of the aqueoussuspension of calcium carbonate, according to the invention, can be usedin the field of paint.

1. The use of homopolymers of acrylic acid and/or water-solublecopolymers of acrylic acid with one or more acrylic, vinyl or allylicmonomers as dispersing agents for aqueous suspensions of mineralparticles issuing from a mechanical and/or thermal reconcentration stepfollowing upon a step of wet grinding without the use of a dispersantand at low concentration in terms of dry matter, characterised in thatthe said agent is a homopolymer of acrylic acid and/or a water-solublecopolymer of acrylic acid with one or more acrylic, vinyl or allylicmonomers having a molecular weight corresponding to a viscosity indexwith a value from 0.08 to 0.80.
 2. The use of homopolymers of acrylicacid and/or water-soluble copolymers of acrylic acid with one or moreacrylic, vinyl or allylic monomers according to claim 1, characterisedin that the said agent is a homopolymer of acrylic acid in a formpartially neutralized or totally neutralized by one or more neutralizingagents having a monovalent function chosen from the group constituted bythe compounds containing alkaline cations, in particular sodium andpotassium, or also lithium, ammonium, or again the aliphatic and/orcyclic primary or secondary amines such as the ethanolamines, mono anddiethylamine or also cyclohexylamine, and possibly by one or moreneutralizing agents having a polyvalent function chosen from the groupconstituted by the compounds containing alkaline-earth divalent cations,in particular magnesium and calcium, or also zinc, and likewise by thetrivalent cations, including in particular aluminium, or also by certaincompounds containing higher-valency cations.
 3. The use of homopolymersof acrylic acid and/or water-soluble copolymers of acrylic acid with oneor more acrylic, vinyl or allylic monomers according to claim 1,characterised in that the said agent is a water-soluble copolymer ofacrylic acid with one or more acrylic, vinyl or allylic monomers chosenfrom among methacrylic acid, itaconic acid, crotonic acid, fumaric acid,isocrotonic, aconitic, mesaconic, sinapic, undecylenic, angelic orcanellic acid, and/or acrylamido methyl propane sulphonic acid in acidor partially neutralized form, or also from among acrylamide,methacrylamide, the esters of acrylic or methacrylic acids such as ethylacrylate, butyl acrylate, methyl methacrylate, phosphate of acrylate ormethacrylate of ethylene or propylene glycol or also again from amongvinylpyrrolidone, vinylcaprolactame, isobutylene, diisobutylene, vinylacetate, styrene, alphamethylstyrene, styrene sodium sulphonate,vinylmethylether, allylamine and its derivatives.
 4. The use ofhomopolymers of acrylic acid and/or water-soluble copolymers of acrylicacid with one or more acrylic, vinyl or allylic monomers according toclaim 3, characterised in that the said agent is a copolymer of acrylicacid in a form partially neutralized or totally neutralized by one ormore neutralizing agents having a monovalent function chosen from thegroup constituted by the compounds containing alkaline cations, inparticular sodium and potassium, or also lithium, ammonium, or again thealiphatic and/or cyclic primary or secondary amines such as theethanolamines, mono and diethylamine or also cyclohexylamine, andpossibly by one or more neutralizing agents having a polyvalent functionchosen from the group constituted by the compounds containingalkaline-earth divalent cations, in particular magnesium and calcium, oralso zinc, and likewise by the trivalent cations, including inparticular aluminium, or also by certain compounds containinghigher-valency cations.
 5. The use of homopolymers of acrylic acidand/or water-soluble copolymers of acrylic acid with one or moreacrylic, vinyl or allylic monomers according to any one of claims 1 to4, characterised in that the said agent is a homopolymer of acrylic acidand/or a water-soluble copolymer of acrylic acid with one or moreacrylic, vinyl or allylic monomers having a molecular weightcorresponding to a viscosity index with a value from 0.20 to 0.60. 6.The use of homopolymers of acrylic acid and/or water-soluble copolymersof acrylic acid with one or more acrylic, vinyl or allylic monomersaccording to any one of claims 1 to 5, characterised in that the saidagent is introduced in the proportion of 0.1% to 2% by dry weight withrespect to the dry weight of mineral material, and preferentially of0.3% to 1.0% by dry weight.
 7. The use of homopolymers of acrylic acidand/or water-soluble copolymers of acrylic acid with one or moreacrylic, vinyl or allylic monomers according to any one of claims 1 to6, characterised in that the mineral particles issuing from a mechanicaland/or thermal reconcentration step following upon a step of wetgrinding without the use of a dispersant and at low concentration interms of dry matter are chosen from among the synthetic calciumcarbonates or the natural calcium carbonates such as chalk, calcite,marble or also dolomite or their mixtures.
 8. A dispersing agent for anaqueous suspension of mineral particles issuing from a mechanical and/orthermal reconcentration step following upon a step of wet grindingwithout the use of a dispersant and at low concentration in terms of drymatter, characterised in that the said agent is a homopolymer of acrylicacid and/or a water-soluble copolymer of acrylic acid with one or moreacrylic, vinyl or allylic monomers having a molecular weightcorresponding to a viscosity index with a value from 0.08 to 0.80.
 9. Adispersing agent for an aqueous suspension of mineral particlesaccording to claim 8, characterised in that the said agent is ahomopolymer of acrylic acid in a form partially neutralized or totallyneutralized by one or more neutralizing agents having a monovalentfunction chosen from the group constituted by the compounds containingalkaline cations, in particular sodium and potassium, or also lithium,ammonium, or again the aliphatic and/or cyclic primary or secondaryamines such as the ethanolamines, mono and diethylamine or alsocyclohexylamine, and possibly by one or more neutralizing agents havinga polyvalent function chosen from the group constituted by the compoundscontaining alkaline-earth divalent cations, in particular magnesium andcalcium, or also zinc, and likewise by the trivalent cations, includingin particular aluminium, or also by certain compounds containinghigher-valency cations.
 10. A dispersing agent for an aqueous suspensionof mineral particles according to claim 8, characterised in that thesaid agent is a water-soluble copolymer of acrylic acid with one or moreacrylic, vinyl or allylic monomers chosen from among methacrylic acid,itaconic acid, crotonic acid, fumaric acid, isocrotonic, aconitic,mesaconic, sinapic, undecylenic, angelic or canellic acid, and/oracrylamido methyl propane sulphonic acid in acid or partiallyneutralized form, or also from among acrylamide, methacrylamide, theesters of acrylic or methacrylic acids such as ethyl acrylate, butylacrylate, methyl methacrylate, phosphate of acrylate or methacrylate ofethylene or propylene glycol or also again from among vinylpyrrolidone,vinylcaprolactame, isobutylene, diisobutylene, vinyl acetate, styrene,alphamethylstyrene, styrene sodium sulphonate, vinylmethylether,allylamine and its derivatives.
 11. A dispersing agent for an aqueoussuspension of mineral particles according to claim 10, characterised inthat the said agent is a water-soluble copolymer of acrylic acid withone or more acrylic, vinyl or allylic monomers in a form partiallyneutralized or totally neutralized by one or more neutralizing agentshaving a monovalent function chosen from the group constituted by thecompounds containing alkaline cations, in particular sodium andpotassium, or also lithium, ammonium, or again the aliphatic and/orcyclic primary or secondary amines such as the ethanolamines, mono anddiethylamine or also cyclohexylamine, and possibly by one or moreneutralizing agents having a polyvalent function chosen from the groupconstituted by the compounds containing alkaline-earth divalent cations,in particular magnesium and calcium, or also zinc, and likewise by thetrivalent cations, including in particular aluminium, or also by certaincompounds containing higher-valency cations.
 12. A dispersing agent foran aqueous suspension of mineral particles according to any one ofclaims 8 to 11, characterised in that the said agent is a homopolymer ofacrylic acid and/or a water-soluble copolymer of acrylic acid with oneor more acrylic, vinyl or allylic monomers having a molecular weightcorresponding to a viscosity index with a value from 0.20 to 0.60.
 13. Amethod of putting into aqueous suspension mineral particles issuing froma mechanical and/or thermal reconcentration step following upon a stepof wet grinding without the use of a dispersant and at low concentrationin terms of dry matter, characterised in that it uses the aqueoussuspension dispersal agent according to any one of claims 8 to
 12. 14. Amethod of putting particles into aqueous suspension according to claim13, characterised in that the aqueous suspension dispersing agentaccording to any one of claims 8 to 12 is introduced in the proportionof 0.1% to 2% by dry weight with respect to the dry weight of mineralmaterial, and preferentially of 0.3% to 1.0% by dry weight.
 15. Anaqueous suspension of mineral particles issuing from a mechanical and/orthermal reconcentration step following upon a step of wet grindingwithout the use of a dispersant and at low concentration in terms of drymatter, characterised in that it contains 0.1% to 2% by dry weight, withrespect to the dry weight of mineral material, of the aqueous suspensiondispersing agent according to any one of claims 8 to 12, andpreferentially 0.3% to 1.0% by dry weight.
 16. An aqueous suspension ofmineral particles according to claim 15, characterised in that themineral particles are chosen from among the synthetic calcium carbonatesor the natural calcium carbonates such as chalk, calcite, marble or alsodolomite or their mixtures.
 17. An aqueous suspension of mineralparticles according to any one of claims 15 to 16, characterized in thatit has a concentration, in terms of dry matter, of at least 60% with aBrookfield viscosity strictly less than 2,000 mPa.s measured at 100 rpmimmediatly after the putting into suspension and a Brookfield viscositystrictly less than 20,000 mPa.s, measured at 10 rpm after eight daysstorage without agitation.
 18. The use of the aqueous suspensionaccording to either one of claims 15 to 17 in the fields of mass fillingand coating of paper as well as those of paint, ceramics, drillingfluids, fillers for synthetic resins and rubbers, detergent and cleaningformulations, cements, plasters and other fields of application in civilengineering and the construction industry.